Sideloading is the process of transferring files between two local devices, in particular between a personal computer and a mobile device such as a mobile phone, smartphone, PDA, tablet, portable media player or e-reader.
And then a little bit later down:
The use of the term “sideloading” to describe downloading and installing an app outside of sanctioned means is controversial and not universally accepted.[1]
Per Wikipedia:
And then a little bit later down:
A rare time Wikipedia is wrong, I never thought I’d see the day